Microvalve

ABSTRACT

A microvalve has at least two pressurized-medium connections means forming a valve seat between the connections, a closure member cooperating with the valve seat, an electrical actuating unit deflecting the closure member, and a membrane which moves the closure member in opposition to he electrical actuating unit and adjoins a space which can be loaded with pressurized medium. The membrane has an area which is substantially reduced relative to the valve seat and is firmly joined to the membrane and also has a pressure-loaded area. The closure member has a ring-shaped pressure-compensation area which is opposite to the membrane and extends radially outwardly of the reduced surface of the membrane and counteracts the pressure loaded area of the membrane, the pressure-loaded area of the membrane and the pressure-compensation area of the closure member are essentially equally large.

BACKGROUND OF THE INVENTION

The invention relates to a microvalve. More particularly it relates to amicrovalve which has pressurized-medium connections and a valve seatinserted between them with which a closure member is associated and isdeflectable by electrical actuating means.

GB 2,155,152 A has already disclosed such a microvalve which is producedin the multilayer structure known from semiconductor technology. Thismicromechanical valve has essentially three layers, of which an inletand an outlet, and also a valve seat are constructed in a silicon baselayer and an intermediate layer adjoins said base layer and also anouter covering layer adjoins the latter. The layers form a spaceproducing the pressurised-medium link between the two connections. Inthis microvalve, the covering layer is at the same time constructed as amembrane into which a closure member belonging to the valve seat isintegrated. When this microvalve is operated, an electrostatic actuatingdevice disposed on the membrane has to overcome not only the forces ofthe resilient membrane but also the fluid pressure present in the inletsince the membrane which closes the valve seat is not compensated withrespect to this pressure. The result of this is that the microvalve issuitable only for relatively low pressures and consequently produces arelatively low hydraulic switching power. The dynamic behaviour of themicromechanical valve is consequently also adversely affected. Thenon-pressure-compensated construction of the microvalve results, inaddition, in relatively large actuating forces and consequently inrelatively expensive actuating devices.

Reference is furthermore made to the publications EP 0,250,948 A2 and EP0,261,972 A2 in which the technology of producing such microvalves isdescribed more precisely and it is explained how three-dimensionalshapes can be machined in multilayer structures so that differentmechanical elements are possible as a result of combining differentstructural details. The microvalve can consequently be constructed as a2- or 3-way valve. The membrane can also be disposed in an intermediatelayer.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amicrovalve which avoids the disadvantages of the prior art and is afurther improvement.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a microvalve of the above mentioned type in which apressure-compensating area acting opposition to a pressure-loadedmembrane is disposed in a spa at a closure member firmly joined to themembrane.

When the microvalve is designed in accordance with the present inventionit has the advantage that it makes possible a staticallypressure-compensated construction of the microvalve in a relativelysimple and inexpensive way. As a result of this pressure-compensatedconstruction, higher pressures can be controlled or lower actuatingforces can be employed. The fluidic power of the microvalve consequentlyincreases appreciably, it also being possible to achieve high dynamicssince only relatively small masses have to be moved. Thispressure-compensated construction is suitable, in particular, forproduction with micromechanical technologies so that, in addition to lowunit costs, a high-precision manufacture and reproducibility of theparts is possible even with small dimensions. The construction of themicrovalve can be ideally tailored to the possibilities of the differentmicromechanical manufacturing technologies. Furthermore, suchmicrovalves can be interconnected as desired and can also be combined toform so-called valve series.

The pressure loaded area of the membrane and the pressure-compensatingarea can be essentially equally large. The size of thepressure-compensating area can be limited by the valve seat. Thediameter of the valve seat can correspond approximately to the effectivediameter of the membrane. These features make various directions ofmovement of the closure member, it being possible for the closure memberto open both in the flow direction and also against the flow direction,and also various types of electrical actuation.

The area and the closure member loaded by the pressure in the outletconnection can be at least approximately as large as the area at thering membrane loaded by the pressure in the recess and determined by theeffective diameter of the membrane. This embodiment, as a result ofwhich a pressure compensation can be achieved not only on the inlet sidebut also on the outlet side is extremely beneficial. In accordance withanother embodiment of the present invention, the movable component ofthe microvalve can be formed as a double annular membrane. Thisembodiment which is particularly well suited for both flow directions,is furthermore advantageous. A drive in both directions can be achieved.When the actuating means are disposed symmetrically above and below themovable component with double annular membrane as a result of whichpower and dynamics can be increased further.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through a microvalve in a simplifiedrepresentation and on an enlarged scale,

and FIGS. 2 to 5 show a second to fifth exemplary embodiment of amicrovalve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a longitudinal section through a single microvalve 10 witha multilayer structure in a considerably enlarged and simplifiedrepresentation, the individual layers being built up from differentmaterials. At the same time, manufacturing technologies are used for theproduction of this multilayer structure such as are known per se fromsemiconductor technology, in particular under the name of silicontechnology, thin-film technology or thick-film technology. Thesetechnologies for producing certain three-dimensional shapes in amultilayer structure and their potential for constructing mechanicalelements determined by structural details are here assumed to be known.

The microvalve 10 has essentially a base layer 11, an intermediate layer12 and a covering layer 13. At the same time, an annular space 15 whichis bounded in the upward direction by the covering layer 13 andcommunicates with an inlet connection 17 via a channel 16 running in theintermediate layer 12 is formed in the intermediate layer 12 by a recess14 in the form of an annular groove. The relatively thin-walled base ofthe recess 14 forms a resilient annular membrane 18 which surrounds acentrally situated layer region 19 which is thick compared with thelatter. The annular membrane 18 is consequently integrated into theintermediate layer 12 and bounded by the space 15 formed by the recess14.

The covering layer 13 has an outlet connection 21 which expands in theinward direction to form a shallow, disc-shaped recess 22. The recess 22forms an annular valve seat 23 on the side facing the intermediate layer12. In the unactuated position of the microvalve 10 shown, a plate-typeclosure member 24 which is attached to the layer region 19 by an area 25which is substantially reduced compared with the diameter of the valveseat 23 rests against the valve seat 23. At the same time, theplate-type closure member 24 consists of a layer additional to theintermediate layer 12 and made of the same or different material. Inthis connection, the thicknesses of the layer region 19 and the closuremember 24 are so chosen that together they correspond to the thicknessof the intermediate layer 12.

With this construction of the microvalve 10, the movable componentconsisting of the annular membrane 18, the layer region 19 and theclosure member 24 has a pressure area 26 whose size is essentiallydetermined by the size of the ring membrane 18. At the same time, on themovable component 18, 19, 24 a pressure compensation area 27 isprovided. The pressure compensation are loaded in the opposite directionand its size is limited, on the one hand, by the valve seat 23 and, onthe other hand, by the area 25. These two areas 26 and 27 are matched toone another in such a way that they are essentially equally large.

An area 30 on top of the plate-type closure member 24 and loaded withthe return pressure p2 is limited by the valve seat 23. An area 31 onthe bottom of the movable component 18, 19, 24, which area is loadedwith the pressure p0, is determined by the effective diameter 32 of theannular membrane 18.

For as complete as possible a pressure compensation at the movablecomponent 18, 19, 24, the areas 30 and 31 must be essentially equallylarge. This assumes that the pressures p0 beneath and p2 above themovable component are essentially equally large. The spaces 22 above and28 beneath the movable component 18, 19, 24 do not, however, necessarilyhave to contain the same medium: for example, the space 22 may contain aliquid, whereas the space 28 is filled with air, under whichcircumstances ambient pressure may prevail in both spaces so that p0 isessentially equal to p2.

Disposed in the base layer 11 in a shallow recess 28 facing theintermediate layer 12 is an electrode 29. It serves as electricalactuating means for the closure member 24 and, in addition, forms anelectrostatically acting drive.

The mode or operation of the microvalve 10 is explained as follows: thepressurised medium flowing in from an inlet connection 17 not shown inmore detail via the channel 16 reaches, with the microvalve 10 notactuated, the space 15 in which the inlet pressure can build upcorrespondingly. This pressure in the space 15 acts, on the one hand,downwards on the pressure area 26 at the membrane 18 and simultaneouslyon the annular pressure-compensation area 27 at the closure member 24.Since these two pressure areas 26, 27 are constructed so as to besubstantially equally large, the movable component 18, 19, 24 iscorrespondingly statically pressure-compensated. Under the influence ofthe restoring force of the resilient annular member 18, the closuremember 24 is in close contact with the valve seat 23 and blocks the linkto the outlet connection 21. This restoring force of the annularmembrane 18 may be very small as a consequence of thepressure-compensated construction of the microvalve 10.

To open the microvalve 10, the electrode 29 is connected to voltage. Asa result, an electrostatic drive for the movable component 19, 24 actsin a manner known per se and the closure member 24 moves downwards, inwhich process it is lifted off the valve seat 23. Pressurised medium cannow flow out of the space 15 to the outlet connection 21.

To close the microvalve 10, the electrostatic drive 29 is switched off.As a result, the closure member 24 again rests on the valve seat 23under the influence of the restoring force of the resilient annularmembrane 18 and consequently blocks the pressurised-medium link. At thesame time, it is assumed that the pressures p2 and p0 on the areas 30and 31 respectively are essentially equally large and consequently apressure compensation also exists in relation to the said areas.

As a result of the pressure-compensated construction of the microvalve10, it is possible that pressures substantially higher than hitherto cannow be controlled and that a relatively weak, and consequentlyinexpensive and space-saving drive can be used as electrical actuatingmeans. The microvalve 10 is therefore suitable for controllingsubstantially larger hydraulic or pneumatic pressures and, in addition,makes higher dynamics possible. At the same time, thepressure-compensation area 31 can also be matched relative to the sizeof the pressure area 30 in such a way that only a partial pressurecompensation is achieved. The pressure areas 30, 31 can also be matchedto one another in such a way that, in addition to the residual staticpressure forces, dynamic forces resulting from the flow can also beallowed for and affect the switching behaviour of the microvalve 10.

FIG. 2 shows a second microvalve 40 which differs from the microvalve 10according to FIG. 1 as follows, identical reference symbols being usedfor identical components.

In the second microvalve 40, the valve seat 41 is disposed at theoutside of the cover plate 13, that is to say downstream of the opening42 in the cover plate 13. The closure member 43 has a stud-type section44 which corresponds to the area 25 and by means of which it passesthrough the opening 42 and is firmly joined at the central layer region19 of the intermediate layer 12. The thickness of the central layerregion 19 may at the same time be as large as the thickness of theintermediate layer 12. The intermediate layer 12 and the covering layer13 are furthermore held at a distance from one another by an additionalseparating layer 45. An annular piezoelectric coating 46 is providedinside the recess 28 on the ring membrane 18 as electrical actuatingmeans for the closure member 43. In the second microvalve 40, on the onehand, the pressure area 26 at the ring membrane 18 and, on the otherhand, the pressure-compensation area 27 at the closure member 43 and theareas 30 and 31 are constructed for a static pressure compensation atthe movable component, and the space 15 is filled with pressurisedmedium extending from the intermediate layer 12 through the separatinglayer 45 and the covering layer 13.

The mode of operation of the second microvalve 40 corresponds inprinciple to that of the first microvalve 10. The annular membrane 18 isactuated upwards, however, by the piezoelectric coating 46 and theclosure member 43 consequently is opened in the flow direction. If thesame pressure exists in the recess 28 in this valve construction as thepressure in the outlet, that is to say downstream of valve seat 41, themovable component consisting of annular membrane 18, layer region 19 andclosure member 43 is essentially pressure-compensated with respect tothe pressures in the inlet and also in the outlet.

FIG. 3 shows a longitudinal section through a third microvalve 50 whichdiffers from the first microvalve 10 only in that a thermoelectriccoating 51 which is provided inside the recess 28 in the region of thering membrane 18 at the intermediate layer 12 is provided as electricalactuating means. The closure member 24 can consequently be actuated inthe same direction of movement as in the case of the first microvalve10, namely downwards from the starting position shown.

FIG. 4 shows a fourth microvalve 60 which differs from the secondmicrovalve 40 shown in FIG. 2 in that a thermofluidic actuation isprovided instead of the piezoelectric actuation. For this purpose, thereis applied in the recess 28 of the base layer 11 a heating resistance 61which heats up when an electric current flows through it. In thisprocess, it heats up the fluid (liquid or gas) enclosed in the recess 28so that the latter expands. As a consequence of the increase in pressurecaused thereby in the recess 28, the annular membrane 18 is deflectedupwards and the closure member 43 opens in the flow direction.

FIG. 5 shows a fifth microvalve 70 which differs from the microvalve 10shown in FIG. 1 in that both the annular membrane and the electricalactuating device are present in duplicate. It contains two additionalintermediate layers 71 and 72. The movable component 19, 24 from FIG. 1is linked via a further central layer region 74 to a second annularmembrane 73 which is constructed in the intermediate layer 72. Providedabove the movable component 19, 24, 74 in the covering layer 13 is afurther electrical actuation 75 which is constructed in the same way asthe electrical actuation 29 underneath the first annular membrane 18.This achieves a completely symmetrical construction of the microvalve70. In particular, a complete pressure compensation is ensured at themovable component 19, 24, 74 in this construction even if the pressuresp0 and p2 differ fairly considerably from one another.

In the case of the microvalve 10, it is assumed on the other hand, thatthe possible difference between p0 and p2 is small, which may possiblynot be guaranteed in every application case.

The electrical actuating means 75 or 29, respectively, present above orbelow the movable component 19, 24, 74 has, in addition, the advantagethat the valve can be both opened and closed by electrical actuation. Inthe case of the microvalve 10, on the other hand, closure takes place asa result of the resilient restoring action of the annular membrane 18.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in amicrovalve with multilayer structure, it is not intended to be limitedto the details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A microvalve, comprising at leasttwo pressurized-medium connections; means forming a valve seat betweensaid connections; a closure member cooperating with said valve seat;electrical actuating means deflecting said closure member; and amembrane which moves said closure member in opposition to saidelectrical actuating means and adjoins a space which can be loaded withpressurized medium, said membrane having an area which is substantiallyreduced relative to said valve seat and is firmly joined to saidmembrane and also having a pressure-loaded area, said closure memberhaving a ring-shaped pressure-compensation area which is opposite tosaid membrane and extends radially outwardly of said reduced surface ofsaid membrane and counteracts said pressure loaded area of saidmembrane, said pressure loaded area of said membrane and saidpressure-compensation area of said closure member being essentiallyequally large.
 2. A microvalve as defined in claim 1, wherein said valveseat has a lateral extension which substantially corresponds to alateral extension of said membrane.
 3. A microvalve as defined in claim1; and further comprising means forming a recess, said connectionsincluding another connection which is not connected with said spaceloaded with a pressurized medium said closure member having an areawhich is loaded by a pressure in said another connection and locatedopposite to said pressure-compensation area, said membrane having asurface which is loaded with a pressure acting in said recess anddetermined by an effective lateral extension of said membrane, saidsurface loaded by a pressure in said another connection beingsubstantially equally large to said surface which is loaded by apressure in said recess.
 4. A microvalve as defined in claim 1, whereinsaid valve seat, said closure member, said membrane are formed in aplurality of layers; and further comprising a base layer, said pluralityof layers including an intermediate layer in which said membrane isformed and which is arranged on said base layer, said layers also havinga covering layer in which said valve seat is formed and which isarranged on said intermediate layer at its side opposite to said baselayer.
 5. A microvalve as defined in claim 1, wherein said membrane isformed as a resilient annular membrane.
 6. A microvalve as defined inclaim 5; and further comprising an intermediate layer, and an additionallayer, said intermediate layer having a ring groove-shaped recess whichforms said space loaded with pressurized medium, said intermediate layerforming said membrane in the region of said recess and also having athicker central layer region, said closure member being provided in saidadditional layer and formed as substantially load-tight platelette.
 7. Amicrovalve as defined in claim 4; and further comprising an intermediatelayer, said membrane and said closure member extending together within athickness of said intermediate layer.
 8. A microvalve as defined inclaim 7; and further comprising a covering layer arranged on saidintermediate layer and forming said valve seat.
 9. A microvalve asdefined in claim 4, wherein said valve seat is formed at an outer sideof said covering layer, said closure member extending through saidcovering layer.
 10. A microvalve as defined in claim 1, wherein saidmembrane constitutes a movable component, said movable component havinga double annular membrane.
 11. A microvalve as defined in claim 10; andfurther comprising two intermediate layers which form said doubleannular membrane and said layer regions, and another intermediate layerwhich forms said valve seat and is located between said first mentionedintermediate layers, said closure member being arranged between centrallayer regions of said first mentioned intermediate layers.
 12. Amicrovalve as defined in claim 10, wherein said actuating means arelocated symmetrically above and below said double annular membrane. 13.A microvalve as defined in claim 1, wherein said actuating means isformed as a piezoelectrically operating coating on said membrane.
 14. Amicrovalve as defined in claim 1, wherein said actuating means is formedas a thermoelectrically operating coating on said membrane.
 15. Amicrovalve as defined in claim 1; and further comprising a base layer onwhich said membrane is arranged, said actuating means including anelectrode arranged in said base layer for electrostatically attractingsaid membrane.
 16. A microvalve as defined in claim 1; and furthercomprising a base layer on which said membrane is arranged, saidactuating means including a heat resistance arranged on said base layerfor thermofluidically deflecting said membrane.
 17. A microvalve asdefined in claim 1, wherein said connections include an inletconnection, said space being connected with said inlet connection.
 18. Amicrovalve as defined in claim 1, wherein said valve seat, said closingmember, said membrane are formed as a silicon-technology producedmultilayer structure.
 19. A microvalve as defined in claim 1, whereinsaid valve seat, said closing member, said membrane are formed as athin-film technology produced multilayer structure.
 20. A microvalve asdefined in claim 1, wherein said valve seat, said closing member, saidmembrane are formed as a thick-film technology produced multilayerstructure.
 21. A microvalve as defined in claim 1, wherein saidmicrovalve is formed as a fuel injection valve.
 22. A microvalve asdefined in claim 1, wherein said microvalve is formed as a servovalve.